1) No, the amount it absorbs is based on the damage done to the minion(s) without the PL
2) Wall, however armor on the PL minion is a good thing as to make that minion take less damage vs FB and COC, thereby letting it have more HP to be able to absorb

However, elven gear that will increase your dex will be helpful on a PL minion. This gear increases your dex, thereby increasing your skill level. I would stay away from items that lower your dex with the exception of a corn (if your PL minion is an enchanter)

IE, I have elven gloves, boots and cloak on my PL minion with the following PL: Phantom Link: 70,292/51,686 (126,525)

You can go one more and put the PL/AoI minion first and the 400AC wall second so that you aren't picked off with MM. All physical attacks will go to the wall, MM attacks will go to the back minion, redirected to the front.